<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
       /* .test {
            width: 150px;
            height: 300px;
            border: 1px solid #ccc;
            margin-top: 100px;
            float: left;
            margin-left: -1px;
        }
        .test:hover {
            border: 1px solid #f40;
            position: relative;
        } */
        .test {
            width: 150px;
            height: 300px;
            border: 1px solid #ccc;
            margin-top: 100px;
            float: left;
            margin-left: -1px;
            position: relative;
        }
        .test:hover {
            border: 1px solid #f40;
            z-index: 1;

        }
    </style>
</head>
<body>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
</body>
</html>